Modern-day agricultural practice requires precise application of various dry granular materials for various purposes. Such materials include fertilizers, pesticides, fungicides, herbicides and seed. For example, dry granular chemicals can be applied to the soil before, during, or after planting. Some may also be applied directly to growing plants long after the planting operation. The type of material to be applied and its application rate depend upon the plants involved, and it will be understood that the materials and application rates can vary widely. After one type of material has been applied, it may be necessary to clean out the applicator and adjust it for application of another material at a different rate.
A variety of applicators for this purpose have been available heretofore. Such applicators usually include metering apertures at the bottom of a hopper through which material is discharged by means of gravity and a feed rotor located inside the hopper above the apertures. U.S. Pat. No. 3,776,430 to the assignee hereof shows one such prior device. U.S. Pat. Nos. 3,128,921 to Henderson and 2,784,881 to Hines are also representative of the in this regard.
Although various granular applicators have been available heretofore, they have not been without certain drawbacks. The applicators of the prior art generally require complete clean-out of the hopper before the metering or feed wheels can be replaced and/or repaired, and are thus not readily adapted for efficient changeover. Material changeover and/or metering wheel changeover can be time-consuming and thus expensive with such applicators. In addition, it may not be possible to accomplish thorough cleanout without at least some disassembly. Some prior applicators are relatively complicated in construction, and are thus expensive to manufacture and difficult to maintain. Further, many of the prior applicators incorporate a relatively long, internal feed rotor together with multiple discharge openings. This arrangement is subject to inaccuracies when the unit is operated on a hill at a tilt because the material tends to collect in one side of the hopper, exposing one end of the feed rotor and thus resulting in uneven or interrupted metering at some of the discharge openings.
A need has thus arisen for a more versatile granular applicator which incorporates a removable metering assembly including interchangeable feed wheels that can be removed and replaced as necessary without emptying the hopper so that the applicator can be readily adapted for applying various granular materials.